Do I Need to Sand a Semigloss Surface Before Applying a Satin Finish?

If the Surface is Unsound

• An unsound surface -- one that is peeling, pitted, scratched or stained with an oil-based contaminant -- must be stripped down to a sound substrate before refinishing. Sanding seldom is sufficient; painting over the edges of sanded-off layers of paint inevitably shows through the finish coat as a series of ripples. Depending upon the substrate, use paint stripper and a steel wool pad or a heat gun and a scraper to remove the unsound coats; next, sand and prepare the exposed substrate, then prime and paint according to the paint manufacturer’s instructions.

Repainting a Sound Surface

• A sound surface is one where the previous paint is still uniformly and entirely attached to the substrate, whatever that might be. Regardless of the appearance of the surface, dulled, sun-bleached or stained with coffee-cup rings, if the preexisting paint -- including a semigloss paint -- is sound, it can be sanded and repainted.

Prepping Gloss, Semi-Gloss and Satin

• The experts at "Popular Woodworking Magazine" note that semigloss and satin paints have flattening agents added that reduce the paint's gloss and that painters must “Pay more attention to doing a thorough sanding if you are using a gloss finish than if you are using one with flatting agents included.” Nonetheless, to ensure that a good mechanical bond is achieved between the preexisting semigloss and the new satin coat, the sanding should be thorough and even.

Sanding Preexisting Paint

• If the semigloss surface is sound, wash it with sugar soap or a similar detergent to remove atmospheric and mechanical contaminants that could have adhered to its surface; even finger grease could spoil the eventual finish. Sand with a fine abrasive paper such as 220 grit to “key” the surface. Keying means to interrupt the smoothness of the semigloss so that the satin paint will have a better chance of adhering. To remove the sanding dust, wipe over the sanded surface with a clean, lint-free rag moistened with mineral spirits, then apply the satin coat according to the manufacturer’s instructions.